Since there is such a wide variety of poly and other types of tarps on the market from which to choose, you want to ensure you get a good tarp for your needs without overpaying. Some tarps are meant for builders and heavy-duty use and may then be more expensive, but may not be what you need around the house. On the other hand, choosing a tarp because it's the cheapest option may mean not protecting what is being covered. Note a few tips for choosing a good poly tarp without overpaying for your needs.
1. Heavy-duty tarps
Typically the thickness of a poly tarp will determine if it's considered heavy-duty, and many that are sold as heavy-duty or builder's tarps are 250 microns or thicker. These heavier tarps are good for keeping out the maximum amount of rain, snow, and other such elements, and their heavier weight also makes them good to use outdoors as they're less likely to blow away. Invest in these for covering over an RV during the off season or protecting your home when you're renovating and have exposed beams or a hole in the roof.
2. Grommet placement
If you're putting down a tarp inside to cover furniture or floors during painting, you may not need any grommets or holes for tie-downs. Tarps without grommets may be cheaper since they don't need to be punched in the production process. However, for a tarp you want to tie down, note the grommet placement. Some are put only at the corners and this can be sufficient for covering firewood, where you can securely tie the tarp to posts of your deck where you store the wood. For covering a roof in rainy or windy weather, you need additional grommets along the side for more tie-downs. The more grommets, the easier it will be to secure the tarp. Invest in a tarp with a higher number of grommets for more inclement weather or outdoor use.
3. Poly versus canvas
A canvas tarp can be a good choice for allowing moisture to pass through, when you don't want your tarp to hold moisture such as when morning dew might collect on firewood you're storing. However, this also means that canvas is not as water-repellant as poly, nor is it as flame resistant. If you're covering a barbecue grill in the off season or something in a garage, you might want to use poly that is noted as being flame-resistant so that your materials are protected from a potential fire. The canvas might also allow rain and snow to seep in to the roof or RV you're covering, so poly can be the better choice in these cases.